Displays of corrugated cardboard or similar material provided with shelves that can bear and display products, for example, in a point of sale, are known in the prior art. Some of these displays comprise a structure formed from a single piece of relatively rigid sheet material with at least two vertical fold lines defining a back wall and two side walls that can be bent along said vertical fold lines in order to be arranged in mutually facing positions which are substantially perpendicular to said back wall, such that said structure can remain upright in an expanded working position. One or more shelves are hingedly joined to the back wall and can be arranged in a position substantially perpendicular to the back and side walls in said expanded position, and support means are arranged for bearing said third panel with respect to the first and second panels in the expanded position.
U.S. Pat. No. 4,271,766 describes a display with shelves of the type described above, in which the mentioned support means for the shelves comprise metal rods extending from another one of the side walls of the structure, and on which the front edges of the shelves rest. However, these metal rods must be manually installed and they prevent the capacity of the display for automatically standing up.
In U.S. Pat. No. 5,193,466 and U.S. Pat. No. 5,366,100, the side walls of the structure are folded inwardly and the support means comprise cords extending from another one of the side walls of the structure. These cords are loose in the flat position and substantially tensed in the expanded position to support the front edges of the shelves.
Patents JP-A-2004049788 and U.S. Pat. No. 7,007,615 disclose a display with shelves in which each shelf comprises a rigid shelf panel and an auxiliary panel provided with diagonal fold lines, acting as the support means for the shelf. The side walls of the structure fold inwardly, the shelf panel folds upwardly with respect to its back edge and the auxiliary panel, which is fixed at its ends to the side walls of the structure and at a central part to the lower part of the shelf panel, folds by bending along the diagonal fold lines.
In some of these known displays with shelves, for example those described in U.S. Pat. No. 4,493,424 and U.S. Pat. No. 6,394,290, the piece of sheet material furthermore includes a horizontal fold line transverse to the vertical fold lines to allow folding the display from an inactive flat position to a compact folded position. The display described in the mentioned U.S. Pat. No. 4,493,424 includes elastic pulling means, such as elastic rubber bands, for pulling on the side walls and applying them against the edges of the shelves to maintain the expanded position of the structure. These pulling means cooperate with a manual action in the standing of the display from the compact folded position to the expanded working position. When displays of this type are in their expanded working position, the shelves are supported on the back wall and, especially, on the side walls of the structure, so the weight of the products supported on the shelves is withstood by the piece of sheet material forming the structure. For this reason, when corrugated cardboard or plastic of considerable thickness is used to build the structure, the inner flutes thereof are arranged parallel to the vertical direction, since this is the direction in which such flutes offer greater structural strength. The side walls are often formed, in at least part of their horizontal extension, by a double or triple ply of corrugated cardboard or plastic to provide the structure with greater strength. These additional plies are typically adhered to the side walls. In some of the mentioned displays, the additional plies of the side walls are formed entirely with the piece of sheet material of the structure from extensions of the side walls bent along vertical fold lines, whereby also achieving that the side walls have smooth front edges, thus preventing the inner structure of the relatively rigid sheet material from being exposed along unappealing cut front edges of the panel of corrugated cardboard or plastic or other relatively rigid sheet material used.
A problem existing in displays with shelves of the prior art provided with horizontal fold lines formed by scored lines is that these scored lines crush the inner structure of the relatively rigid sheet material, weakening their bearing capacity in the vertical direction. Furthermore, the subsequently bending of the relatively rigid sheet material around the mentioned scored lines further weakens the bearing capacity of the structure. When the material used is corrugated cardboard or plastic, the horizontal fold lines crush the flutes of the corrugated cardboard or plastic in a direction transverse to the longitudinal direction thereof, so the continuity of the flutes is destroyed in horizontal fold lines and the vertical bearing capacity of the panel of structure is seriously weakened. Furthermore, when there are sections of the panel having a structure with two or more plies, due to the differences in the radii of curvature between the innermost plies and the outermost plies, bending them along horizontal fold lines formed by scored lines is virtually impossible without crushing, breaks and/or tears occurring in the corrugated cardboard or plastic or other relatively rigid sheet material. These problems are substantially the same in the case of using foam board or another similar material, although it does not have a predominant strength direction.
The mentioned U.S. Pat. No. 5,193,466 describes a product display with shelves comprising a structure formed by a panel having a structure of corrugated cardboard with vertical fold lines delimiting a single ply back wall and two triple ply side walls. The display folds along a horizontal fold line affecting only the back wall, and it prevents the folding problems in the triple ply side walls by providing cuts which divide the side walls into two parts; an upper part and a lower part. In order to couple the upper and lower parts of each side wall, a flange projects from the intermediate ply of the upper part that is configured to fit into a recess formed in the intermediate ply of the lower part. This solution preserves the structural continuity of the flutes of the corrugated cardboard in the side walls, and thereby the structural bearing capacity in the vertical direction. However, this solution requires manual assembly of the display to stand it up in its expanded position, and it is incompatible with a display that can be stood up automatically in cooperation with pulling means included therein.
In addition, foldable structures for a display made up of several panels linked with one another such that they can adopt a flat position, in which the panels are substantially coplanar, and an expanded position, in which the panels define a prism, such as a cube or a rectangular prism, are known on the market. However, these foldable structures for a display must be handled manually in order to go from the flat position to the expanded position, since they cannot be stood up automatically to the expanded position.